Most robotic manipulator structures include some type of base member which is often immovably connected to a mounting in a floor or similar structure, and a turret or turntable portion which rotates relative the base member to alter the position of the payload or working portion of the robotic manipulator. Quick starts and stops of such rotating turntable, as well as sudden changes in the effective loading of extendable robotic arms and the like, often transfer the impact of such movements in the form of sudden shocks and vibrations in the form of rocking vibrations and shocks to said turntable, and more particularly to the main bearing of the base. Additionally, external vibrations and shocks can be imposed on a robotic manipulator, such as by other equipment operating nearby. Due to the inherent compliances and clearances within the interacting parts at the interface of the turntable and the base (especially at the main bearing thereof), often a limited amount of displacement can be introduced into the system by such various shocks, vibrations, and jolts. In applications such as robotic manipulators where accurate and steady movement is often critical to successfully accomplishing the task at hand, even a relatively small amount of backlash or slack can be very harmful. If the amount of compliance in a system is relatively substantial, the robotic manipulator is much less reliable and accurate in its functions and, possibly, inappropriate for delicate operations. In modern applications which rely immensely on operations which require precise movements, such slack or backlash becomes increasingly more intolerable.
An example of a relatively simple robotic arm having a bearing support is shown in U.S. Pat. No. 4,546,233, which issued to H. Yasuoka on Oct. 8, 1985. In particular, this patent describes an arc-welding robot which includes a stationary table fixed to a floor, and having a rotary table mounted for rotation thereon by a pair of bearings. As shown in the drawings, the bearings are spaced apart longitudinally to support the rotary table in a rotatable manner on the stationary table. While the Yasuoka structure includes a tension spring to reduce the load bearing on the arm tilting motor, it does not include any structure intended to dampen the inherent shocks and jolts which the rotary table will convey to the stationary table during normal use.
Similarly, U.S. Pat. No. 4,392,776, issued to L. Y. Shum on July 12, 1983, describes a robotic manipulator structure including a base which rotatably supports a first swinging arm for rotation relative thereto. The first swinging arm is carried at its proximate end by a hollow shaft which is supported for rotation relative the base by a pair of spaced bearings. Like the Yasuoka structure, the Shum robotic manipulator structure utilizes the main rotator bearings to support a rotatable manipulator structure without any means for damping the inherent shocks and jolts which the robot's moveable arm and rotatable mechanism will inherently impose on the stationary base thereof.
Consequently, despite the universal knowledge in the industry that unwanted displacement or compliances in the moving parts of a robot are becoming increasingly more intolerable as the need for precision increases, there remain problems in effectively and efficiently eliminating such inherent displacement or compliances resulting from shocks, jolts and vibrations commonly encountered by rotator bearings in the base of such robotic manipulators.